Transcript for Hands-Free Technology May Be Biggest Driving Distraction

Surprising finding about distracted driving. We're not supposed to hold our phones behind the wheel. But a new study shows that hands-free technology that lets you talk or text with both hands on the wheel may create more distractions. Abc's david kerley tested it out. Reporter: Some estimates ask that half of accidents like this are caused by distracted drivers. this is going to be a great look for me. I'm about to look really strange for science. I'm going to put the chin strap on. Reporter: All to prove whether all of those voice-activated gadgets automakers are putting in cars make me a safer or more distracted driver. When they start turning black, that's when the electrodes are starting to connect to my brain. Wired up with electrodes on my face and this attractive skull cap with even more, we tested to see how much my brain can do. I click a butt button with my thumb. And using the same thing with a speech to text system. Listening to and answering e-mails. Would you want to meet in my office? Repeat. Reply. Reporter: Reply. What would you like to say? Reporter: Friday, 1:00, in your office. Send. Turns out that speech-to-text system that lets you keep your hands on the wheel and your eyes on the road, caused more distractions than anything else the researchers tested. Your brain is so overloaded with these speech-to-text task, that you have little residual capacity to tend to the roadways. Reporter: The aaa, who sponsored this study, wants restrictions. The speech-to-text should be used or limited to use for drivers when the vehicle is stopped. Reporter: A surprising finding, that our brains can't do it all, even when our eyes are on the road. David kerley, abc news, landover, maryland. Just got to keep your eyes on

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